Various "straight line" cappers or sealing machines for applying closures onto containers are disclosed in U.S. Pat. Nos. 3,143,835; 3,274,748; 3,438,174; 4,199,914; 4,279,115; and 4,716,708. Those machines generally include a linear horizontal conveyor which carries filled but still open containers in a row through a closure feeding device, a closure applicator, and a closure sealer in sequence. The closure feeding device typically feeds or presents the closures to the moving containers by a chute or slide mechanism. As the containers are moved by the conveyor, the leading edge of the presented closure is engaged by the leading edge of the top of the container. The movement of the container pulls the closure from its feed position so that it is seated on the container. A closure applicator then presses the closure onto the container and/or rotates the closure onto the container to seal it.
At operating rates of about 1200 containers per minute and higher, the reliability and accuracy at which previous machines engage and seat the closures upon the containers diminishes. The impact of the leading edge of the container on the closure may "throw" or dislodge the closure so that it does not seat on the container. Another difficulty is that the closure may end up "cocked" or improperly seated on the container, as a result of which it cannot be sealed properly by the subsequent closure applicator and sealing means.
Other types of "straight line" sealing machines are disclosed in U.S. Pat. Nos. 3,392,505 and 4,696,143. The '505 patent is directed to a dual head apparatus for applying closures to containers. A transfer head removes closures from a dispenser and transfers them to an inserter head, which in turn applies the closures to containers. During the transferring step, the closure is reoriented about a transverse axis so that it is presented with its bottom side facing toward the opening of the container to which it will be applied. The complexity of the closure pickup and transfer mechanism of such machines does not lend itself to effective high speed capping.
The '143 patent is directed to a container capping apparatus which includes a rotating carriage that receives closures from a conveyor and applies them to containers moving on a second conveyor. The rotating carriage has a tangential velocity that exceeds the linear velocity of the container conveyor, and thus the speed of the containers on the conveyors is wholly controlled by the rotating carriage. That machine likewise is not capable of effective high speed capping.
In Herzog U.S. Pat. No. 5,054,260, issued Oct. 8, 1991, titled "High Speed Sealing Machine" there is disclosed a sealing machine in which closures are applied by an applicator wheel to containers moving on a straight line. The wheel rotates in a plane parallel to the line of movement of the containers, and has a plurality of closure carriers or holders around its periphery. It is driven at a rate such that the linear speed of the carriers and closures matches that of the containers. Closures are fed to the closure carriers by a star wheel or notched wheel. The star wheel preferably rotates about an axis which is transverse to the axis of rotation of the applicator wheel and which is parallel to the line of movement of the containers on the conveyor. While that machine is capable of applying closures at rates of 1,000 to 2,000 closures per minute, depending upon the type of closure and container, nevertheless it cannot apply some closures at rates as high as would be desired.
Thus there remains a need for an improved closure applicator and sealing machine that can be operated at speeds heretofore not reliably attain able, while still providing good seal integrity with an acceptably low rate of rejections.